King Leopold II was the exclusive owner of the Congo Free State from 1885 to 1908. The movie is set in 1907. During Leopold's ownership it has been estimated that the population was decreased by as much as 50% while profits for some years were as much as 100%. The first resource harvested was ivory but the next, and most profitable, was rubber. Torture, killing, and mutilations were used to such an extent on the population enslaved by Leopold that the rubber crop was referred to as "Red Rubber".
Filmed at Twentieth Century-Fox studios, Los Angeles and Calabassas, California. A second film unit was sent to Africa for background shots.
Although the movie is set in Africa, in the scene where John and Ellen are walking across the rope bridge, the waterfall shown in rear projection is actually Vernal Falls in Yosemite National Park in California.
The movie takes place in the Congo Free State in 1907. King Leopold II, the exclusive owner of the Congo Free State from 1885 to 1908, once said, "It is a question of creating a new state, as big as possible, and of running it. It is clearly understood that in this project there is no question of granting the slightest political power to the negroes (sic). That would be absurd."
The rifle that Mitchum carries is a Westley Richards. The bolt handle has a bone knob on the end. Westley Richard is the only company that made rifles that way. The caliber is probably .318 Westley Richards. Rifles of that size would be of that caliber. Their other caliber was the .425 Westley Richards.